Exhaust-gas turbochargers serve in a known manner for increased performance of piston engines by increasing an air flow and fuel flow rate per combustion cycle. Such an exhaust-gas turbocharger causes this by increasing the pressure in the intake tract so that for the combustion, a larger amount of air and hence more oxygen is available for a correspondingly larger amount of fuel. In the exhaust-gas turbocharger itself, a rotatably supported shaft is arranged which carries in a known manner a compressor wheel on the one end, and a turbine wheel on the other end. Due to the shaft's high rotational speeds which can be achieved during the operation of the exhaust-gas turbocharger, the shaft has to be sufficiently lubricated to prevent a quick wear. To be able to ensure the lubricity on a long-term basis, the lubricant used for lubricating the shaft is filtered, wherein even in case of a clogging of the filter, a sufficient lubrication of the shaft has to be ensured to avoid damage.
From U.S. Pat. No. 7,040,874 B1, a charging device of the generic kind is known in which in a lubricant supply channel, a filter element for filtering the lubricant is arranged. Should the filter element be clogged during the operation thereby losing its filtering effect, a plunger-like safety valve is provided which opens and releases a bypass line bypassing the filter element. In this case, the lubricant flows indeed unfiltered to the bearing device, however, it can be avoided that the bearing device is only insufficiently lubricated.
From US 2006/0193734 A1, a further bearing device of the generic kind is known.